1. Field of the Invention
The present invention relates to a mechanical hinged connecting device, and more particularly to a hinge joint for connecting two members of a hinged structure and adapted to be selectively locked in different relative positions.
2. Description of the Prior Art
Various hinge devices of this type are already known which are commonly used for selectively locking in different relative positions coupled structure members, for instance of folding ladders, seats, pieces of furniture or the like.
Such hinge devices are generally comprised by two concentrically arranged plates mounted for relative pivoting motion around a hinge axis and comprising an unlockable selective locking mechanism for relatively securing the two plates, and accordingly the structure members connected thereto, in several predetermined angular positions.
The locking mechanisms in such hinge devices generally consist of a ratchet wheel cooperating with a releasable pawl device. Other known locking mechanisms embody a locking device of the spring-bolt type mounted on one of the plates for cooperation with notches or recesses forming bolt-clasps which are formed in the periphery of the other plate, said notches being arranged in angularly spaced relationship and distributed so as to correspond to the determined locking positions of the hinge.
Such locking devices of the spring-bolt type can be moved relatively to the first supporting plate in a generally radially extending direction with respect to the hinge axis upon actuation by a release lever means which is hingedly mounted on said first plate for pushing the spring-bolt locking member towards its unlocked position against the biasing force of a return spring, additional locking devices being eventually provided on the second plate for latching the actuating lever in an unlocked position of the hinge.
Said actuating levers or handles present many drawbacks. Since they have to be designed so as to actuate the locking member against the biasing force of a strong return spring, they are generally of a large construction, whereby they contribute to increase the total weight of the hinge. Moreover, since the biasing force of the return spring is directly exerted upon said lever, the angular maneuvering range of the protruding or handling portion of said lever results in problems of accessibility and transmission of actuating forces and also in risks for the user to have his fingers or his palm become hinged between said handle and the adjacent structure member of the hinge. Additionally, the locking device for locking such levers has also to be broadly dimensioned and do not permit the smooth operation of the mechanism.